RE: [PATCH 2/3 v2] iommu/fsl: Enable default DMA window for PCIedevices

[Sethi Varun-B16395]

> -----Original Message-----
> From: Bhushan Bharat-R65777
> Sent: Wednesday, October 16, 2013 10:43 PM
> To: Sethi Varun-B16395; joro@xxxxxxxxxx; iommu@xxxxxxxxxxxx
> foundation.org; linuxppc-dev@xxxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; Yoder Stuart-B08248; Wood Scott-B07421;
> alex.williamson@xxxxxxxxxx
> Subject: RE: [PATCH 2/3 v2] iommu/fsl: Enable default DMA window for PCIe
> devices
> 
> 
> 
> > >
> > >
> > > > -----Original Message-----
> > > > From: Sethi Varun-B16395
> > > > Sent: Wednesday, October 16, 2013 4:53 PM
> > > > To: joro@xxxxxxxxxx; iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx; linuxppc-
> > > > dev@xxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Yoder
> > > > Stuart-B08248; Wood Scott-B07421; alex.williamson@xxxxxxxxxx;
> > > > Bhushan
> > > > Bharat-R65777
> > > > Cc: Sethi Varun-B16395
> > > > Subject: [PATCH 2/3 v2] iommu/fsl: Enable default DMA window for
> > > > PCIe devices
> > > >
> > > > Once the PCIe device assigned to a guest VM (via VFIO) gets
> > > > detached from the iommu domain (when guest terminates), its PAMU
> > > > table entry is disabled. So, this would prevent the device from
> > > > being used once it's
> > > assigned back to the host.
> > > >
> > > > This patch allows for creation of a default DMA window
> > > > corresponding to the device and subsequently enabling the PAMU
> > > > table entry. Before we enable the entry, we ensure that the
> > > > device's bus master capability is disabled (device quiesced).
> > > >
> > > > Signed-off-by: Varun Sethi <Varun.Sethi@xxxxxxxxxxxxx>
> > > > ---
> > > >  drivers/iommu/fsl_pamu.c        |   43
> ++++++++++++++++++++++++++++---
> > > -----
> > > >  drivers/iommu/fsl_pamu.h        |    1 +
> > > >  drivers/iommu/fsl_pamu_domain.c |   46
> > > ++++++++++++++++++++++++++++++++++++---
> > > >  3 files changed, 78 insertions(+), 12 deletions(-)
> > > >
> > > > diff --git a/drivers/iommu/fsl_pamu.c b/drivers/iommu/fsl_pamu.c
> > > > index
> > > > cba0498..fb4a031 100644
> > > > --- a/drivers/iommu/fsl_pamu.c
> > > > +++ b/drivers/iommu/fsl_pamu.c
> > > > @@ -225,6 +225,21 @@ static struct paace *pamu_get_spaace(struct
> > > > paace *paace,
> > > > u32 wnum)
> > > >  	return spaace;
> > > >  }
> > > >
> > > > +/*
> > > > + * Defaul PPAACE settings for an LIODN.
> > > > + */
> > > > +static void setup_default_ppaace(struct paace *ppaace) {
> > > > +	pamu_init_ppaace(ppaace);
> > > > +	/* window size is 2^(WSE+1) bytes */
> > > > +	set_bf(ppaace->addr_bitfields, PPAACE_AF_WSE, 35);
> > > > +	ppaace->wbah = 0;
> > > > +	set_bf(ppaace->addr_bitfields, PPAACE_AF_WBAL, 0);
> > > > +	set_bf(ppaace->impl_attr, PAACE_IA_ATM,
> > > > +		PAACE_ATM_NO_XLATE);
> > > > +	set_bf(ppaace->addr_bitfields, PAACE_AF_AP,
> > > > +		PAACE_AP_PERMS_ALL);
> > > > +}
> > > >  /**
> > > >   * pamu_get_fspi_and_allocate() - Allocates fspi index and
> > > > reserves
> > > subwindows
> > > >   *                                required for primary PAACE in
> the
> > > secondary
> > > > @@ -253,6 +268,24 @@ static unsigned long
> > > > pamu_get_fspi_and_allocate(u32
> > > > subwin_cnt)
> > > >  	return (spaace_addr - (unsigned long)spaact) / (sizeof(struct
> > > > paace));  }
> > > >
> > > > +/* Reset the PAACE entry to the default state */ void
> > > > +enable_default_dma_window(int liodn) {
> > > > +	struct paace *ppaace;
> > > > +
> > > > +	ppaace = pamu_get_ppaace(liodn);
> > > > +	if (!ppaace) {
> > > > +		pr_debug("Invalid liodn entry\n");
> > > > +		return;
> > > > +	}
> > > > +
> > > > +	memset(ppaace, 0, sizeof(struct paace));
> > > > +
> > > > +	setup_default_ppaace(ppaace);
> > > > +	mb();
> > > > +	pamu_enable_liodn(liodn);
> > > > +}
> > > > +
> > > >  /* Release the subwindows reserved for a particular LIODN */
> > > > void pamu_free_subwins(int liodn)  { @@ -752,15 +785,7 @@ static
> > > > void __init
> > > > setup_liodns(void)
> > > >  				continue;
> > > >  			}
> > > >  			ppaace = pamu_get_ppaace(liodn);
> > > > -			pamu_init_ppaace(ppaace);
> > > > -			/* window size is 2^(WSE+1) bytes */
> > > > -			set_bf(ppaace->addr_bitfields, PPAACE_AF_WSE,
> 35);
> > > > -			ppaace->wbah = 0;
> > > > -			set_bf(ppaace->addr_bitfields, PPAACE_AF_WBAL,
> 0);
> > > > -			set_bf(ppaace->impl_attr, PAACE_IA_ATM,
> > > > -				PAACE_ATM_NO_XLATE);
> > > > -			set_bf(ppaace->addr_bitfields, PAACE_AF_AP,
> > > > -				PAACE_AP_PERMS_ALL);
> > > > +			setup_default_ppaace(ppaace);
> > > >  			if (of_device_is_compatible(node, "fsl,qman-
> portal"))
> > > >  				setup_qbman_paace(ppaace,
> QMAN_PORTAL_PAACE);
> > > >  			if (of_device_is_compatible(node, "fsl,qman"))
> diff --
> > > git
> > > > a/drivers/iommu/fsl_pamu.h b/drivers/iommu/fsl_pamu.h index
> > > > 8fc1a12..0edcbbbb
> > > > 100644
> > > > --- a/drivers/iommu/fsl_pamu.h
> > > > +++ b/drivers/iommu/fsl_pamu.h
> > > > @@ -406,5 +406,6 @@ void get_ome_index(u32 *omi_index, struct
> > > > device *dev);  int pamu_update_paace_stash(int liodn, u32 subwin,
> > > > u32 value); int pamu_disable_spaace(int liodn, u32 subwin);
> > > >  u32 pamu_get_max_subwin_cnt(void);
> > > > +void enable_default_dma_window(int liodn);
> > > >
> > > >  #endif  /* __FSL_PAMU_H */
> > > > diff --git a/drivers/iommu/fsl_pamu_domain.c
> > > > b/drivers/iommu/fsl_pamu_domain.c index 966ae70..dd6cafc 100644
> > > > --- a/drivers/iommu/fsl_pamu_domain.c
> > > > +++ b/drivers/iommu/fsl_pamu_domain.c
> > > > @@ -340,17 +340,57 @@ static inline struct device_domain_info
> > > > *find_domain(struct device *dev)
> > > >  	return dev->archdata.iommu_domain;  }
> > > >
> > > > +/* Disable device DMA capability and enable default DMA window */
> > > > +static void disable_device_dma(struct device_domain_info *info,
> > > > +				int enable_dma_window)
> > > > +{
> > > > +#ifdef CONFIG_PCI
> > > > +	if (info->dev->bus == &pci_bus_type) {
> > > > +		struct pci_dev *pdev = NULL;
> > > > +		pdev = to_pci_dev(info->dev);
> > > > +		if (pci_is_enabled(pdev))
> > > > +			pci_disable_device(pdev);
> > > > +	}
> > > > +#endif
> > > > +
> > > > +	if (enable_dma_window)
> > > > +		enable_default_dma_window(info->liodn);
> > > > +}
> > > > +
> > > > +static int check_for_shared_liodn(struct device_domain_info *info)
> {
> > > > +	struct device_domain_info *tmp;
> > > > +
> > > > +	/*
> > > > +	 * Sanity check, to ensure that this is not a
> > > > +	 * shared LIODN. In case of a PCIe controller
> > > > +	 * it's possible that all PCIe devices share
> > > > +	 * the same LIODN.
> > > > +	 */
> > > > +	list_for_each_entry(tmp, &info->domain->devices, link) {
> > > > +		if (info->liodn == tmp->liodn)
> > > > +			return 1;
> > > > +	}
> > > > +
> > > > +	return 0;
> > > > +}
> > > > +
> > > >  static void remove_device_ref(struct device_domain_info *info,
> > > > u32
> > > win_cnt)  {
> > > >  	unsigned long flags;
> > > > +	int enable_dma_window = 0;
> > > >
> > > >  	list_del(&info->link);
> > > >  	spin_lock_irqsave(&iommu_lock, flags);
> > > > -	if (win_cnt > 1)
> > > > -		pamu_free_subwins(info->liodn);
> > > > -	pamu_disable_liodn(info->liodn);
> > > > +	if (!check_for_shared_liodn(info)) {
> > >
> > > One query; Do we really need to check for this?
> > >
> > [Sethi Varun-B16395] Yes, just a sanity check to ensure that there are
> > no more devices linked to this LIODN and we can disable it.
> 
> Varun, trying to understand this; say there are two device under a PCI
> controller which share the LIODN of PCI controller, So both of the device
> must be unbound from kernel driver and then bind both to VFIO.
> 
> Now when guest terminated then remove_device_ref() will be called for
> both of device but the sanity check will pass for the one which will be
> called later, is this right?
> 
Yes, when the first device is detached PAMU LIODN table entry is not disabled. The LIODN would only be disabled once all devices are detached.

-Varun


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